Ok, I just put on a magnaflow catback system (15646) and it is way too loud. It is fine idling, but driving it rattles my brains! Also, I had ordered a new cat, a high flow model, but it hasn't gotten here yet so I pounded a 1" hole through the combs in my old cat until the new one gets here, hopefully next week. Would this cause it to be any louder and resonate like a ****? I would think the high flow cat would be about the same?

So my question is, what can I do to get it quieter? My old muffler was completely rusted around the pipe and I had suspected my stock cat was plugged, hence the new one. The reason I went with this setup was that it was cheaper than replacing it with all factory components again...the dealer wanted $550 just for a cat!

Thanks guys.